The pack rides during the sixth stage of the Tour de France cycling race over 181 kilometers (112.5 miles) with start in Brest and finish in Mur-de-Bretagne Guerledan, France, Thursday, July 12, 2018. (AP Photo/Peter Dejong)

The pack rides during the sixth stage of the Tour de France cycling race over 181 kilometers (112.5 miles) with start in Brest and finish in Mur-de-Bretagne Guerledan, France, Thursday, July 12, 2018. (AP Photo/Peter Dejong)

Musicians perform on the side of the road as the pack with Belgium's Greg van Avermaet, wearing the overall leader's yellow jersey, centre, rides during the sixth stage of the Tour de France cycling race over 181 kilometers (112.5 miles) with start in Brest and finish in Mur-de-Bretagne Guerledan, France, Thursday, July 12, 2018. (AP Photo/Peter Dejong)

The pack rides during the sixth stage of the Tour de France cycling race over 181 kilometers (112.5 miles) with start in Brest and finish in Mur-de-Bretagne Guerledan, France, Thursday, July 12, 2018. (AP Photo/Peter Dejong)

The pack rides during the sixth stage of the Tour de France cycling race over 181 kilometers (112.5 miles) with start in Brest and finish in Mur-de-Bretagne Guerledan, France, Thursday, July 12, 2018. (AP Photo/Peter Dejong)

Ireland's Daniel Martin crosses the finish line to win the sixth stage of the Tour de France cycling race over 181 kilometers (112.5 miles) with start in Brest and finish in Mur-de-Bretagne Guerledan, France, Thursday, July 12, 2018. (AP Photo/Peter Dejong)

Ireland's Daniel Martin celebrates as he crosses the finish line to win the sixth stage of the Tour de France cycling race over 181 kilometers (112.5 miles) with start in Brest and finish in Mur-de-Bretagne Guerledan, France, Thursday, July 12, 2018. (AP Photo/Christophe Ena )

MUR DE BRETAGNE, France (AP) — Sometimes in cycling the bike can be the rider's biggest enemy.

Tour de France contenders Tom Dumoulin and Romain Bardet both lost significant time in the overall standings after spokes on their wheels snapped near the uphill end of Stage 6 on Thursday.

Both title hopefuls were left behind by the rest of the top riders as they increased the pace hunting for the win that finally went to Daniel Martin of Ireland.

Dumoulin said his bike broke when he knocked into Bardet near the foot of the second of two two-kilometer ascents up the Mur de Bretagne to the finish line.

"I hit the back wheel of Bardet when there was the movement in the peloton and I couldn't avoid it," the Dutch rider said. "I needed to change wheel and chase to the finish as hard as possible but it was very difficult."

Dumoulin and his Sunweb team compounded the mechanical mishap by getting a 20-second penalty when Dumoulin stayed too close to the team car while trying to catch the pack, thereby benefiting from its draft that pulled him along.

"I knew I wouldn't make it back so it was about limiting the time loss," Dumoulin said. "I'm disappointed of course, I would have liked to be in a better position on (general classification) but that's how it is."

Dumoulin and Bardet entered the three-week race among the chosen few riders considered strong enough to challenge four-time champion Chris Froome.

Dumoulin, the time trial world champion and 2017 Giro d'Italia winner, started the stage 44 seconds ahead of Froome, but finished just behind him. Froome trails race leader Greg Van Avermaet by 1:02. Dumoulin is one more second behind.

Bardet was already trailing Froome, and after losing 28 seconds is now 1:45 off the leader's pace after he broke his back wheel and had to change bikes with Tony Gallopin.

"Then I had to chase and that effort was fatal. It's never good to lose time," said Bardet, who has finished on the podium in the past two Tours. "There are a lot of twists on the Tour and this time luck was not on our side."

Martin took the win for UAE Emirates after he broke away on the final kilometer, winning the 181-kilometer (112-mile) leg that started in the western port city of Brest in over four hours.

"I saw the moment. I had really good legs and when I went my legs kept coming and coming," Martin said. "I knew if I could get a gap it would be difficult to close from behind."

Pierre Latour crossed the line second followed by Alejandro Valverde in third.

Van Avermaet, a BMC support rider for Porte, kept the yellow jersey for a third straight day.

Froome's teammate Geraint Thomas moved into second place overall at three seconds behind Van Avermaet after snatching two additional bonus in an intermediate bonus sprint.

Martin was one of several team leaders along with former Tour winner Vincenzo Nibali and two-time runner-up Nairo Quintana who were caught off-guard by an attack by Quick-Step midway through the stage during a straightaway that was exposed to crosswinds.

A group of around 40 riders including Froome opened up a gap of over a minute, but Martin and the rest hustled back.

This was the first summit finish of this Tour. After the relatively flat first nine days, the race will head south and into the Alps and then the Pyrenees Mountains.

Friday's flat 231-kilometer leg from Fougeres to Chartes is the longest stage of this Tour.